β-delayed γ spectroscopy of neutron rich Na27,28,29

The low-energy level structure of the exotic Na isotopes Na27,28,29 has been investigated through β-delayed γ spectroscopy. Detailed level structure of Na28,29 has been obtained through βγ and βγγ coincidence measurements. The low-lying levels populated in Na27 by β decay were found to corroborate well with the in-beam data from the literature. Half-lives of the parent nuclides, Ne27,28,29, were measured using β fragment as well as fragment βγ coincidences and compared to previous measurements. The β-delayed one- and two-neutron emission branching probabilities have been obtained from the γ activities of the grand daughter nuclei. A comparison of the level schemes and the β-decay branching ratios is made with shell-model predictions, both with and without intruder configurations, to understand the transition from normal-dominant to intruder-dominant excitations in these neutron-rich nuclei approaching the island of inversion. © 2006 The American Physical Society.